Let FrameSelection::localCaretRect on a text input field avoid synchronous layout.

Source/core/editing/VisibleUnits.h

 /*
  * Copyright (C) 2004 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 13 matching lines @@
  */
 
 #ifndef VisibleUnits_h
 #define VisibleUnits_h
 
 #include "core/editing/EditingBoundary.h"
 #include "platform/text/TextDirection.h"
 
 namespace blink {
 
+class LayoutRect;
+class PositionWithAffinity;
+class RenderObject;
 class Node;
 class VisiblePosition;
 
 enum EWordSide { RightWordIfOnBoundary = false, LeftWordIfOnBoundary = true };
 
 // words
 VisiblePosition startOfWord(const VisiblePosition &, EWordSide = RightWordIfOnBoundary);
 VisiblePosition endOfWord(const VisiblePosition &, EWordSide = RightWordIfOnBoundary);
 VisiblePosition previousWordPosition(const VisiblePosition &);
 VisiblePosition nextWordPosition(const VisiblePosition &);
@@ skipping 42 matching lines @@
 VisiblePosition startOfDocument(const VisiblePosition &);
 VisiblePosition endOfDocument(const VisiblePosition &);
 bool isStartOfDocument(const VisiblePosition &);
 bool isEndOfDocument(const VisiblePosition &);
 
 // editable content
 VisiblePosition startOfEditableContent(const VisiblePosition&);
 VisiblePosition endOfEditableContent(const VisiblePosition&);
 bool isEndOfEditableOrNonEditableContent(const VisiblePosition&);
 
+// Rect is local to the returned renderer
+LayoutRect localCaretRectOfPosition(const PositionWithAffinity&, RenderObject*&);
+
 } // namespace blink
 
 #endif // VisibleUnits_h